1. Field of the Invention
The present invention relates in general to the field of information handling system displays, and more particularly to a method and system for switching a DDC display host.
2. Description of the Related Art
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Information handling system users typically interact with information handling systems through input and output devices, such as a display, keyboard and mouse. However, in some instances, user interaction with an information handling system is rare, such as during testing of systems or with servers that process network information. For example, a test rack typically supports operation of plural information handling systems that repeatedly run test operations to determine system failure rates with the system operations monitored by a common keyboard, mouse and display. As another example, a blade server supports plural blade information handling systems that process network information with a blade server having a common keyboard, mouse and display that selectively interface a user with each blade. Typically, a common keyboard, mouse and display interface with plural information handling systems through a KVM (keyboard video mouse) switch. A user selects the information handling system to interface with the keyboard, mouse and display and the KVM switch interfaces the signals so that the selected information handling system communicates with the keyboard, mouse and display.
KVM switches are effective at cycling video signals in a VGA format between different host information handling systems but have difficulty cycling video signals in a Digital Visual Interface (DVI) format. The DVI-I standard transfers video information as a serial signal to the display sent through a TDMS channel. The information handling system determines the type of display and other configuration information with EDID information sent from the display through a relatively slow speed DDC channel. If EDID information is unavailable, the host information handling system will typically default to the communication of video information in the VGA format by driving a VGA port instead of the DVI port. Since the KVM switch does not maintain a continuous DDC channel from a selected host information handling system to the display as the host selection changes, a new host selection by the KVM switch often provides a VGA signal instead of a DVI signal, or no signal at all. For instance, the DDC interface provides too slow of an exchange of EDID information so that cycling between host information handling systems results in an unselected host attempting to read EDID information. Since the returned information is invalid, the host information handling system may switch to a unconnected display port which results in no video display to the user. To return the display, the correct EDID information must then typically be read at POST, driver load and hardware redetect in order for the DVI display to be properly driven.